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Deserialization of Untrusted DataWeakness · CWE-502

CVE-2026-8727

HIGH · 7.1 CVSS v4.0 Published 2026-05-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
75/100
Remediation priority · High
Remotely reachable

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The Crawler extension passes the X-T3Crawler-Meta response header from crawled URLs directly to PHP's unserialize(). An attacker controlling a crawled endpoint can inject arbitrary serialized PHP objects, leading to Remote Code Execution on the TYPO3 server. Exploitation requires administrative privileges to configure a crawler-enabled page and trigger the crawl via a Scheduler task.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The TYPO3 Crawler extension has a PHP object injection vulnerability where the X-T3Crawler-Meta response header from crawled URLs is passed directly to the unsafe unserialize() function. An attacker with administrative access can configure a crawler task to fetch a malicious endpoint they control, which responds with a crafted serialized PHP object in the header, triggering arbitrary code execution on the TYPO3 server.

MitigationDisable or restrict the Crawler extension if unused; otherwise, apply any available vendor patch that adds input validation/sanitization before passing the header value to unserialize(). Until patched, monitor for unauthorized Scheduler task creation.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
High
Authentication
X
User interaction
A
Scope
X

CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:A/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify TYPO3 Crawler extension is installed
    In TYPO3 backend, go to Admin Tools > Extensions and look for 'Crawler' in the list of installed extensions. Alternatively, check the file system at typo3conf/ext/ for a crawler directory.
    Affected if The Crawler extension is present and enabled in TYPO3.
  2. Determine Crawler extension version
    In the Extensions list in TYPO3 backend, view the Crawler extension details to see its version number. Compare this version against any official TYPO3 security advisories for the fix version of this vulnerability.
    Affected if The installed version has not been patched for CVE-2026-8727.
  3. Check for unauthorized Scheduler tasks using the Crawler
    In TYPO3 backend, go to Scheduler > Scheduled tasks and review any tasks with the Crawler module (look for task types like 'CrawlerQueueExecute', 'CrawlerMultiProcess', or similar). Look for tasks with suspicious URLs pointing to unfamiliar domains.
    Affected if There are crawler-related Scheduler tasks configured to fetch URLs from untrusted or attacker-controlled sources.
  4. Inspect crawler extension configuration for malicious URL patterns
    Query the TYPO3 database table 'tx_crawler_configuration' (or similar crawler config tables) for any configuration entries containing suspicious or external URLs. Use: SELECT * FROM tx_crawler_configuration WHERE config LIKE '%http%'
    Affected if Crawler configurations contain URLs pointing to domains you do not control or recognize.
  5. Review web server and TYPO3 logs for X-T3Crawler-Meta headers
    Check Apache/Nginx access logs for requests containing 'X-T3Crawler-Meta' headers, and check TYPO3 log files (typo3temp/var/logs/) for any unserialize() errors or suspicious activity related to the crawler.
    Affected if Logs show X-T3Crawler-Meta headers being processed or PHP object injection errors.

You are affected if the TYPO3 Crawler extension is installed, enabled, and running without the CVE-2026-8727 patch, especially if untrusted Scheduler tasks can fetch external URLs.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable or restrict the Crawler extension if unused; otherwise, apply any available vendor patch that adds input validation/sanitization before passing the header value to unserialize(). Until patched, monitor for unauthorized Scheduler task creation.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-8727 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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